Determine how wide and how tall you want your shelves to be. Add up the width of each block and subtract from the shelf width.
Decide how many filler space strips you will need and divide by the remaining shelf space. The filler strips don't have to be even, you have things sitting on your shelves at different spacing.
Take blocks #1 and #2. Add filler between to space them apart.
Then add filler on each side of those.
Add filler to the top of that section you just made to make the
height of the shelves.
Next, take block #3 and add filler to the top to make the height of the shelves, then add filler to the sides to take you to the left half of the shelf.
Do block #4 next adding the filler strips to the side to take you to the right side of the shelf and then to the top to take you to the height of the shelves.
You can make the "shelf" a little taller and wider to be "safe" on the measurement and trim them all down to the same size when you finish them all. A little "safeguard" that will save your sanity later.
Just have fun and find a lot of treasures to fill your shelves with.